package com.dragons.qrcode.utils;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.http.HttpServletResponse;

import org.springframework.util.StringUtils;

/**
 * 返回文件流到浏览器
 */
public class ResponseFileUtil {

    /**
     * 返回前台文件流进行展示
     *
     * @param filePath            要返回的文件具体路径
     * @param contentType        例如："image/png"
     * @param response
     */
    public static void responseFileForShow(String filePath, String contentType, HttpServletResponse response)
            throws Exception {
        ResponseFileUtil.responseFile(filePath, contentType, false, response);
    }

    /**
     * 返回前台文件流进行下载
     *
     * @param filePath            要返回的文件具体路径
     * @param contentType        例如："application/x-download;charset=utf-8"
     * @param response
     */
    public static void responseFileForLoad(String filePath, String contentType, HttpServletResponse response)
            throws Exception {
        ResponseFileUtil.responseFile(filePath, contentType, true, response);
    }

    /**
     * 使用response返回文件流
     *
     * @param filePath        要返回的文件具体路径
     * @param contentType    contentType类型
     *                         例如："application/x-download;charset=utf-8"
     *                         例如："image/png"
     * @param isLoad        true时下载,false时展示
     * @param response        借助response进行流的返回
     */
    public static void responseFile(String filePath, String contentType, boolean isLoad, HttpServletResponse response)
            throws Exception {
        // 声明工具类
        BufferedInputStream in = null;
        BufferedOutputStream out = null;

        try {
            // 若路径为空
            if (StringUtils.isEmpty(filePath)) {
                throw new Exception("invalid filepath of null.");
            }

            // 没找到文件
            File file = new File(filePath);
            if (!file.exists()) {
                throw new Exception("file not exist in path [" + filePath + "]");
            }

            // 输出文件流到浏览器
            in = new BufferedInputStream(new FileInputStream(filePath));
            out = new BufferedOutputStream(response.getOutputStream());

            // 设置MineType类型
            response.setContentType(contentType);

            // 如果是下载,指定文件名称
            if (isLoad) {
                String fileName = file.getName(); // 获取文件名
                response.setHeader("Content-disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
            }

            byte[] buffer = new byte[8192];
            int count = 0;
            while ((count = in.read(buffer, 0, 8192)) != -1) {
                out.write(buffer, 0, count);
            }

            out.flush();
            file = null;
        } catch (Exception e) {
            throw e;
        } finally {
            // 关闭输入输出流
            closeStream(in, out);
        }
    }

    /**
     * 关闭输入输出流
     */
    public static void closeStream(InputStream in, OutputStream out) {
        if (null != in) {
            try {
                in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        if (null != out) {
            try {
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
